1. Field of the Invention
This invention relates to the reactivation of catalysts (particularly amorphous base and crystalline aluminosilicate catalysts) used in hydrocarbon conversion reactions. More particularly, the invention is directed to a method for reactivating said catalysts which have become damaged, i.e., "permanently" deactivated, due to excessive heat and/or steam during hydrocarbon conversion operation and which are no longer capable of regeneration by combustion of carbonaceous deposits thereon, or by the usual chemical processes.
2. Description of the Prior Art
The use of catalysts to effect hydrocarbon conversion processes, such as cracking, hydrocracking and reforming is well known. These catalysts include amorphous types, crystalline types and mixed amorphous types. Regardless of the type of catalyst used, these hydrocarbon conversion reactions result in the deposition on the catalyst of a carbonaceous deposit, commonly called coke, and other contaminants such as inorganic oxides. These deposits cover the surface and fill the pores of the catalyst, with consequent decline in catalytic activity. Under conditions of operation, it is necessary to terminate conversion operations after a relatively short time, for example, five to fifteen minutes onstream, and then to restore the activity of the catalyst by burning off or chemically removing the contaminant in a regeneration stage. Methods of regenerating such "temporarily" deactivated catalysts are well known. However, it has been found that, after repeated exposure to hydrocarbon feed particularly under severe conditions such as cracking or hydrocracking, the catalysts become so deactivated that conventional removal of the accumulated coke and oxide deposit does not result in the catalyst regaining an appreciable or adequate percentage of its original activity. During the long exposure to hydrocarbon conversion conditions, the catalysts become fouled by contaminants which cannot be removed by the ordinary regeneration processes. This deactivation is referred to as "permanent" deactivation. Unless satisfactory means are found for restoring to activity the catalyst or portions thereof which are "permanently" deactivated, the catalyst must be replaced.
The term "permanent" as used herein with respect to deactivated catalysts should be understood to relate to a deactivated hydrocarbon-conversion catalyst which cannot be restored to satisfactory catalytic efficiency through the ordinary regeneration processes such as calcining or chemical treatment.
Various methods have been suggested for reactivation of permanently deactivated hydrocarbon-conversion catalysts. For example, U.S. Pat. No. 3,256,205, issued June 14, 1966, to Constabaris et al., teaches that a permanently deactivated hydrogenation catalyst having a supported Group VIII metal can be "rejuvenated" by treatment with strong acid, having a pH of 2 or lower, prior to the usual regenerative step. U.S. Pat. No. 3,451,942, issued June 24, 1969, issued to Bertolacini, discloses a rejuvenating process involving the separate steps of treatment with nitrogen-oxide-affording material, treatment with oxygen, and treatment with hydrogen. U.S. Pat. No. 3,533,959, issued Oct. 13, 1970, to Miale et al., uses a chelating agent capable of reacting with aluminum in order to reactivate deactivated zeolite catalysts. U.S. Pat. No. 3,684,738, issued Aug. 15, 1972, to Chen, treats certain zeolite catalysts of specific silica/alumina mole ratio and specific pore size with hydrogen ions. While some of these prior art methods have been quite satisfactory in some limited instances, others failed to give good results or have been economically unattractive. There are heretofore not been a simple, relatively inexpensive method of reactivating permanently deactivated hydrocarbon-conversion catalysts, which is applicable to substantially all of the various catalysts in current commercial use.
It is therefore an object of this invention to provide a method for reactivating permanently deactivated hydrocarbon-conversion catalysts, which would be relatively simple in operation and economically attractive. It is a further object of this invention to provide a reactivating method which would be applicable to a broad spectrum, i.e., substantially all of the hydrocarbon-conversion catalysts in current use. Other objects of this invention will become apparent from the following discussion.